BALTIMORE (AP)  Officer William Porter was poised and calm as he testified in his own defense Wednesday, telling jurors that he didn”t call an ambulance for Freddie Gray because Gray was alert, appeared uninjured and didn”t complain of any pain or wounds in the back of a police van.

Instead, Gray only said “yes” when Porter offered to get him medical aid, the officer testified. Porter said he suggested to the van driver, Officer Caesar Goodson, that Goodson take Gray to the hospital because he knew a prisoner claiming injury would be turned away from jail.

But “I can”t tell Officer Goodson what to do,” Porter said when asked why he didn”t do more to ensure that Gray went to the hospital immediately.

Porter, who was driving a patrol car, responded to calls for assistance at some of the van stops. Porter said that during the fourth stop, he went inside the back of the van and helped Gray, who was handcuffed and shackled, from the floor onto the bench. Porter said Gray wasn”t limp, and was able to support himself with his legs.

The fourth stop is crucial in Porter”s case because prosecutors say Gray was already injured by the time he arrived there, and that Porter”s failure to call a medic contributed to Gray”s death. Defense attorneys say Gray was injured later in the ride.

“Freddie Gray wasn”t injured at stop four or five, it”s that simple,” Porter said. “Had he been injured, I would have called a medic.”

Prosecutors also say that by not buckling Gray into a seat belt during that stop, Porter was criminally negligent. The department requires detainees to be buckled up and the policy was updated just days before Gray”s arrest, leaving no ambiguity about whether a prisoner should be belted in.

Porter told the jury that the wagon is “pretty tight” and said that of his 200 arrests involving the transport van, he has never belted in a prisoner.

Porter added that it would have been Goodson”s responsibility to buckle Gray into a seatbelt and he didn”t know if Goodson did so at the fourth stop because he left the scene before as the driver was closing the van doors.

Goodson faces the most serious charge stemming from Gray”s death: second-degree “depraved-heart” murder. His trial is next month.

As Porter spoke from the witness stand, facing the jury box, the jurors listened intently, some leaning forward and scribbling notes.

Porter, the first of six officers to go on trial, said he only realized Gray was hurt when the van reached the police station. Porter said Gray was unresponsive “with mucus around his nose and mouth.”

He called Gray”s name  which elicited responses at previous stops  but this time Gray was silent. Porter told jurors the experience was “a very traumatic thing for me.”

Porter faces manslaughter, assault, misconduct in office and reckless endangerment charges. If convicted on all of the charges, the maximum penalty he faces is about 25 years.

Porter said that during the fourth stop, Gray made eye contact with him and spoke “in a regular tone of voice.”

“He never made a complaint of pain or an injury,” Porter said. “In order to call for an ambo I need age, sex, location and complaint of injury. He wouldn”t give me a complaint of injury.”

Gray was a 25-year-old black man who died a week after suffering a spinal injury at some point during a 45-minute ride in the back of the van. His death set off protests and a riot in the city, and became a rallying cry for the Black Lives Matter movement.

Porter, who is also black, told jurors that when Gray was arrested, he overheard him screaming and mentioning something about needing an inhaler. When asked if Gray said he couldn”t breathe at the van”s fourth stop, Porter said, “absolutely not.”

A police investigator previously testified that Porter told her that Gray said he couldn”t breathe during the van ride. But Porter testified Wednesday that the investigator was mistaken, and that he only heard Gray say that when he was arrested, not when he was in the van.

Porter, who was the defense”s second witness, testified for more than four hours before Officer Zachary Novak, who was present during Gray”s arrest and when the wagon arrived at the police station. Novak was the one who ultimately called an ambulance.

Novak told the jury that by April 12, the day Gray was hurt, he hadn”t seen an updated seat belt policy that had been emailed to all department employees, nor had it been read aloud at roll call.

Novak also told jurors that when it comes to seat belting prisoners, in his experience only 10 percent of all detainees are buckled in.

“More often than not people are not seat belted in wagons,” he said.

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This story has corrected the day of the week to Wednesday, not Tuesday.